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MODEL ID runware:ace-step@v1.5-base
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ACE-Step v1.5 Base

ACE-Step v1.5 Base is an open-source music generation foundation model built on a hybrid LLM planner and Diffusion Transformer architecture. It generates full tracks from text prompts with support for voice cloning, lyric editing, remixing, cover generation, and compositions up to 10 minutes. It supports over 50 languages and runs on consumer hardware with under 4GB VRAM.

ACE-Step v1.5 Base

API Options

Platform-level options for task execution and delivery.

taskType

string required value: audioInference

Identifier for the type of task being performed

taskUUID

string required UUID v4

UUID v4 identifier for tracking tasks and matching async responses. Must be unique per task.

outputType

string default: URL

Audio output type.

Allowed values 3 values

outputFormat

string default: MP3

File format for the generated audio.

Allowed values 3 values

webhookURL

string URI

Specifies a webhook URL where JSON responses will be sent via HTTP POST when generation tasks complete. For batch requests with multiple results, each completed item triggers a separate webhook call as it becomes available.

Learn more 1 resource

deliveryMethod

string default: sync

Determines how the API delivers task results.

Allowed values 2 values
Returns complete results directly in the API response.
Returns an immediate acknowledgment with the task UUID. Poll for results using getResponse.
Learn more 1 resource

uploadEndpoint

string URI

Specifies a URL where the generated content will be automatically uploaded using the HTTP PUT method. The raw binary data of the media file is sent directly as the request body. For secure uploads to cloud storage, use presigned URLs that include temporary authentication credentials.

Common use cases:

  • Cloud storage: Upload directly to S3 buckets, Google Cloud Storage, or Azure Blob Storage using presigned URLs.
  • CDN integration: Upload to content delivery networks for immediate distribution. 
// S3 presigned URL for secure upload
https://your-bucket.s3.amazonaws.com/generated/content.mp4?X-Amz-Signature=abc123&X-Amz-Expires=3600

// Google Cloud Storage presigned URL
https://storage.googleapis.com/your-bucket/content.jpg?X-Goog-Signature=xyz789

// Custom storage endpoint
https://storage.example.com/uploads/generated-image.jpg

The content data will be sent as the request body to the specified URL when generation is complete.

ttl

integer min: 60

Time-to-live (TTL) in seconds for generated content. Only applies when outputType is 'URL'.

includeCost

boolean default: false

Include task cost in the response.

numberResults

integer min: 1 max: 20 default: 1

Number of results to generate. Each result uses a different seed, producing variations of the same parameters.

Inputs

Input resources for the task (images, audio, etc). These must be nested inside the inputs object.
inputs » audio

audio

string

Audio input (UUID or URL).

Generation Parameters

Core parameters for controlling the generated content.

model

string required value: runware:ace-step@v1.5-base

Identifier of the model to use for generation.

Learn more 3 resources

positivePrompt

string required min: 2 max: 3000

Text prompt describing elements to include in the generated output.

Learn more 2 resources

negativePrompt

string min: 2 max: 3000

Prompt to guide what to exclude from generation. Ignored when guidance is disabled (CFGScale ≤ 1).

Learn more 1 resource

duration

float min: 0 max: 300 step: 0.1 default: 60

Duration of the generation in seconds. Total frames = duration × fps.

seed

integer min: 0 max: 2147483647

Random seed for reproducible generation. When not provided, a random seed is generated in the unsigned 32-bit range.

steps

integer min: 0 max: 1000 default: 100

Total number of denoising steps. Higher values generally produce more detailed results but take longer.

Learn more 1 resource

CFGScale

float min: 1 max: 30 step: 0.01 default: 10

Guidance scale. Higher values follow the prompt more closely at the cost of quality.

Learn more 1 resource

strength

float min: 0 max: 1 step: 0.01 default: 0.5

Fraction of steps using the input source instead of generated output.

Learn more 3 resources

Settings

Technical parameters to fine-tune the inference process. These must be nested inside the settings object.
settings » bpm

bpm

integer min: 30 max: 300

Beats per minute. If not set, the model decides automatically.

settings » coverConditioningScale

coverConditioningScale

float min: 0 max: 1 step: 0.01 default: 1

Fraction of steps using source-audio conditioning.

settings » guidanceType

guidanceType

string default: apg

Controls how guidance is applied during generation.

Allowed values 2 values
Adaptive Projected Guidance.
Classifier-Free Guidance.
settings » keyScale

keyScale

string

Musical key and scale in '{Note}{Accidental} {Mode}' format (e.g. 'C major', 'F# minor', 'Bb major').

settings » lyrics

lyrics

string

Song lyrics, typically formatted like a lyrics website.

settings » repaintingEnd

repaintingEnd

integer

End time in seconds for repaint region. Requires input audio. Values beyond audio duration append new audio.

settings » repaintingStart

repaintingStart

integer

Start time in seconds for repaint region. Requires input audio. Negative values prepend audio before the start.

settings » timeSignature

timeSignature

integer

Beats per measure. Empty string lets the model decide.

Allowed values 4 values
settings » vocalLanguage

vocalLanguage

string default: en

ISO 639-1 language code for vocals. 'unknown' for instrumental or auto detection.

Allowed values 51 values
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